This invention is directed toward a composite air spring. More specifically, the air spring is comprised of a structurally supported piston that maintains the cylindrical configuration under high force.
Composite air springs are well known in the art. Examples of known air springs are illustrated in U.S. Pat. Nos. 3,033,558, 3,043,582, 3,596,895, 4,718,650, 4,787,606, 4,798,369, 5,201,500, 5,326,082, 5,535,994, 5,382,006, and 5,671,907.
Some of these air springs are provided with internal bumpers. Internal bumpers prevent the upper and lower retainers from striking one another when the force exerted upon the bumper is greater than spring of the elastomeric sleeve.
Rolling lobe air springs, such as illustrated in U.S. Pat. No. 5,535,994, are provided with pistons. The pistons provide both a means for mounting the air spring and a surface for the rolling lobe sleeve to travel upon when the air spring is subjected to forces upon the upper surface of the air spring. The piston is subjected to multiple forces. Radial forces are transmitted to the piston by means of contact with the upper retainer or transmitted through the bumper. The piston is subjected to circumferential forces by the sleeve folding down and embracing the sides of the piston.
To withstand the forces acting upon the piston, pistons have been formed from metal, such as in U.S. Pat. Nos. 5,382,006 and 5,671,907. Pistons have also been formed of hard thermoplastic. To enable the thermoplastic piston to withstand the forces to which it is subjected, the pistons have been formed with very thick walls, such as shown in U.S. Pat. No. 4,718,650, or formed in a nested tube configuration. Both of these methods require the use of large amounts of material to achieve the desired durability and endurance characteristics required of the piston.
A third common construction is the formation of ribs extending from the inner piston wall to an internal column. However, as the sleeve rolls down the piston, due to the circumferential forces generated, the location of the piston reinforced by the rib remains rigid while the locations of the piston between the ribs would exhibit a spring-like reaction. The constant flexing of the piston sidewalls due to the alternating rigid and spring-like areas may lead to cracking of the piston.
The inventive air spring and piston disclosed has a construction yielding reduced manufacturing costs, and a piston capable of withstanding greater burst and crush strengths and greater endurance under the subjected circumferential and radial forces.
In accordance with the present invention, a new and improved air spring assembly is provided.
An object of the present invention is an improved composite air spring with reduced manufacturing costs.
Another object of the present invention is an improved composite air spring wherein the circumferentially forces acting upon the piston are absorbed by the piston.
Another object of the present invention is an improved composite air spring wherein under high forces the cylindrical configuration of the piston is maintained.
The objects of the present invention are realized by an air spring construction comprising spaced end members and an internal bumper that absorbs shock upon the air spring experiencing severe deflections, and prevents the spring from total collapse.
Another aspect of the invention is an air spring comprising a piston formed with supporting and strengthening members that move with the compressive forces acting upon the piston during operation of the air spring.
Another aspect of the invention is an air spring comprising a piston formed with internal ribs that float, or move, with the compressive forces acting upon the piston during operation of the air spring.